Description of the Prior Art
A number of devices have been suggested for feeding out particle material, such as movable arms or blades which rotate or oscillate to and fro and are usually intended for use in combination with one or more screws. It is also usual to use only a screw arrangement to feed out the material. Other examples are feeders with slats or scrapers which bring with them the material to an outlet opening, the slats or scrapers may move to and fro or they may be disposed on a continuous belt. A problem encountered with most known feeding devices is that they do not give a uniform flow of material down through the container seen in cross section. Instead the flow may be greater on one side than on the other or the flow in the middle of the container may differ from that at the walls. The problem is particularly serious when the material is to be treated with a treating agent in gaseous or liquid form at or without increased temperature since the quality of the material will be uneven due to the fact that it will be treated for varying lengths of time as a result of varying flow rates seen in a cross section of the container. An example of such an application is in the pulp industry when steaming chips. Before being fed into a digester the chips are treated with steam in a chip bin in order to heat the chips to a desired high temperature and at the same time to remove air from the interior of the chips. It will be understood that with the varying flow rates described in the chip bin, the steamed chips fed out will vary in quality so that the chips will have different temperatures and varying amounts of retained air.
GB-948 444, NO-129 085 and EP-A1-0 247 682 describe various devices for discharging particle material. The known devices have one or more of the drawbacks discussed above. EP-A1-0 247 682 is not useful for chips, either, since it utilizes eccentric rings which feed the material in two opposite directions towards adjacent outlet openings at both sides of each ring. Owing to the oblong thin shape of the chip it is not possible to repeatedly change its feeding direction when a uniform flow is to be obtained.